Electrical machinery brush holder



Aug. 25, 1964 Filed Nov. 14 1960 ELECTRICAL MACHINERY BRUSH HOLDER 2Sheets-Sheet 1 INVENTOR.

ATTORNEY Aug. 25, 1964 N. A. MILLAR ELECTRICAL MACHINERY BRUSH HOLDER 2Sheets-Sheet Filed Nov. 14, 1960 INVENTOR. 77ml 77/111121 ATTORNFYUnited States Patent 3,146,365 ELECTRICAL MACHINERY BRUSH HOLDER Neal A.Miller, La Grange Park, Ill., assignor to General Motors Corporation,Detroit, Micln, a corporation of Delaware Filed Nov. 14, 1960, Ser. No.68,731 3 Claims. (Cl. 310-246) This invention relates generally to astructure associated with the brushes of electric motors and generatorsand more particularly to means for holding one or more brushes incontact with a commutator.

In designing a brush holder for the brushes of electrical machinerythere are several factors which must be considered. First, a simple buteffective means must be provided to engage the brush held by the brushholder and press the brush against its associated commutator. As thebrushes wear, this brush engaging means must maintain the brush incontact with the commutator and it is desirable that the pressureapplied to the brush by such means be non-variable irrespective of brushlength.

Since these brushes are replaced from time to time as they wear out, themeans normally holding the brushes in contact with the commutator mustbe capable of being retracted so that the old brush can be removed and anew one inserted. Brush engaging means previously available have notbeen made to be easily retractable. Furthermore, such priorconstructions have required that the service personnel hold the brushengaging means in the retracted position with one hand while removingand replacing the brushes with the other hand. The above procedure isawkward because when the removal and replacement of brushes requiresboth hands of the person servicing the electric machine he has greatdifficulty holding the brush engaging means in a retracted positionwhile replacing the brushes. Naturally, the stiffer the springs holdingthe brushes in contact with the commutator, the more awkward anddiflicult changing the brushes becomes. The present invention providesnovel means for holding the brush holding means retracted to therebyfacilitate removal and replacement of brushes.

In prior brush engaging construction, the fingers which were biased bythe springs against the brushes to hold them in contact with thecommutator were commonly pivoted at one end, usually by means of arivet, pin or the equivalent. Such construction, however, resulted inconsiderable rivet or pin and spring breakage. While such rivets arestill used, the present construction additionally provides for slidingmovement of the pivoted ends of the fingers. This sliding movementallows the springsto locate the fingers so that the brush springfunctions normally and without restriction. The sliding arrangement alsoallows shock and vibrating loads applied to the motor armature toproduce a slight sliding action instead of an impact action as wasproduced when the ends of the fingers were pivotally anchored by rivets,etc. It has been found that this sliding feature practically eliminatesrivet and spring failures.

' Because of operational and functional difiiculties which sometimesoccur in electrical machinery of the kind concerned with here, there isalways the possibility that socalled fiashovers (arcing) may occur inthe vicinity of the brush holders. It is important that the functioningparts associated with the brush holder such as the means holding thebrushes against the commutator be protected from these flashovers orarcing so that they continue to be operable after a flashover occurs.The present invention includes as an important part thereof a case whichencloses the main functioning part of the means which holds the brushesagainst the commutator, i.e., the spring. In tests carried out utilizingthe brush engaging means,

3,146,365 Patented Aug. 25, 1964 it has been found that after severeflashovers there was no damage to the spring or other parts of the brush.the utilization of split brushes in combination with means individuallybiasing each brush wafer against the commutator. This latter feature hasthe advantage of providing positive contact at all times of each brushwafer with the commutator thereby eliminating erratic commuation andreducing or eliminating commutator maintenance.

It is an object of this invention to provide means associated with anelectrical brush holder which will hold the brushes against a commutatorwith constant nonvariable pressure regardless of brush length.

It is a further object of this invention to provide means for lockingthe brush engaging means in a retracted position to facilitate theremoval and replacement of commutator brushes.

It is a further object of the invention to provide a unique pivotalmeans in which the brush engaging means is slidable when retracted toengage in a detent against which it is yieldably held by the spring alsoacting to apply the pressure to the brushes.

For a fuller understanding of the above and other ob jects of thisinvention, reference may be made to the accompanying detaileddescription and the drawings in which:

FIGURE 1 is a view in elevation with certain parts in section of a brushholder including the brush holder stud mounting the brush holder on anelectrical machine and with the means for holding the brushes againstthe commutator shown in the retracted position.

FIGURE 2 is a View similar to FIGURE 1 except that the brush engagingfingers are shown holding the brushes against the commutator.

FIGURE 3 is a top view of the brush holder including the brush engagingmeans.

FIGURE 4 is a sectional view taken substantially on the line 4-4 ofFIGURE 2 illustrating details of the novel sliding pivot means for thebrush engaging fingers.

FIGURE 5 is a View taken substantially on the line 5-5 of FIGURE 2showing details of the constant pressure springs which serve to bias thebrush engaging fingers thereagainst and which also serve to yieldablyhold the fingers in their retracted position when it is desired tochange out the brushes.

FIGURE 6 is an end view of an electric motor showing how the brushholders are mounted on the motor frame and the brushes engage thecommutator of the motor.

Referring first to FIGURE 6, there is shown an electric motor indicatedgenerally by the numeral 2 which includes a frame 4. Mounted forrotation within the frame 4 is the motor armature which includes itscommutator 6. Mounted at circumferential locations about the armature 6are four brush holders each indicated by the numeral 8. These brushholders 8 are secured to the motor frame 4 by insulating brush holderstuds 10.

Referring now to FIGURES 1, 2 and 3 it will be observed that each brushholder 8- has provided at one end thereof an opening 12 for mounting iton its brush holder stud 10. At its opposite end there is provide a slot14 in which is slidably mounted a split brush consisting of two waferseach indicated by a numeral 16. The brush wafers 16 as noted in FIGURES1 and 2 engage and make electrical contact with the commutator 6 attheir ends 18. The opposite ends of waters 16 have electrically securedthereto the usual shunt leads 20 in turn secured at their opposite endsto a common terminal (see particularly FIGURE 3).

Mounted on each brush holder 8 is a brush holder spring cell'which isindicated generally by a numeral 22. This cell 22 may be secured to thebrush holder in any suitable manner. ,In the present instance it may bedone. by passing a bolt, stud or spindle 23through the rivet 50 and" thebrush holder; The cell 22 includes a frame or case 24 having a base 26,opposite sides 28 and 30, and a longitudinally extending detent tab 32forming an extension of the base 261' Mounted'side byside between theopposite sides 28 and; 30-of case 24on rollers or spools 34 are a-pairof non-cumulative force springs 36 which resemble rolls of metal tapewoundon spools 34. This is the force utilized to;hold the brush wafers16 against thecommutator andiis of the-same magnitude regardless ofextended length as long as there is at least one turn of the coilremaining on the spools 34. The

outsiderends 38' of each spring 36 areriveted to a brush engaging fingerintermediate the ends of the associated finger.E'ach'fingewttlisprovided with a brush engaging portion 42 at one endthereof and a straight portion 4-4 which .is pivotally but slidablyanchored in a pivoting assembly 46. Eachpivoting assembly 46 includestwo blocks 4'8whichare pivotally secured'side by side betweenthe sides28 and 30 by a rivet 50. E'ach'block 48 is provided with" a guide. track52in which an end 44 of the associated finger 40 is longitudinallyslidable.

The operation of the brush engaging means is as follows: ReferringtoFIG. 2, it will be observed that the spring 36 by reason of its tendencyto wind on the roller or spool 34 causes the finger 40, including thebrush engaging portion 42",. to engage the outer ends of the brushwafers 16 16', each finger 40 may be individually retracted by pulling,back on its brush engaging end 42' so that the'end 44 of finger 40slides in its guide 52 until it engages the detent 32 against whichit'will be yieldably held by the tension, in spring 3,6. These fingers40 are shown in their retractedtposition in FIGURE 1. After the brushhas beenremoved and replaced, the fingers may again be moved to theiroperative position against thev outer ends of the brush wafers by simplypulling outwardly on the brush engaging portions'42 so that the end 44nov longer engages in the detent, 32. I

From the foregoing. descriptiomit may be appreciated that a simple butextremely effective brush holder spring cell has been provided whichliseasily adaptable to many brush holders for electrical machinery. It alsohas the desirablefeature of providing constant and uniform pressure tohold the brushes against the commutator, As previously emphasized, thebrush engaging fingers are easily retractable to a locked position tofacilitate changing out of the motor brushes;

I claim:

1. Cellular means for holding a brush in contact with a commutatorcomprising a supporting case, a brush engaging finger mounted in saidcase and having a free brush engaging portion extending therefrom, aspring secured to said finger and to said case adaptedvto cause. saidfinger to exert a non-variable pressure on the brush it is adapted tocontact when said case is secured in juxtaposed relation thereto, andmeans to lock said finger in a retracted position in order to remove andreplace the brush normally engaged thereby including guide meansslidably guiding said finger and pivotally secured to said case and adetent on the opposite side of the point of pivotal connection of saidguide means to saidcase from" said brush engaging portion to which anendof said finger is movable and against which said end is yieldably heldby said spring when said finger is retracted.

2. Cellular meansfor holding a brush in contact with a commutatorcomprising asupporting case, a brush engaging finger mounted in saidcase and having a free brush engaging portion extending therefrom, aspring whose bias is the same irrespective of its deflection secured tosaid finger and to said case adapted to cause said finger to exert aconstant pressure on the brush it is adapted to contact when said caseis secured in juxtaposed relation thereto, and means to lock said fingerin a retracted position in order to remove and replace the brushnormally engaged thereby including guide means slidably guiding saidfinger and pivotally secured to said case, and a detent'on the oppositeside of the point of piovtal connection of said guide means to said casefrom said brush engaging portion to which'an end of said finger ismovable and against which said end is yieldably held by said spring whensaid finger is retracted.

3. In combination with an electrical machine havinga commutator, abrushholder mounted adjacentsaid commutator, a brush mounted in saidbrush holder and engaging said commutator, means for holding said brushincontact With said commutator comprising a brush engaging finger havinga free brush engaging portion extending therefrom, a guide for saidfinger slidably supporting said finger intermediate the ends thereof,and a springadapted to bias said finger to cause said finger to exert aconstant presure on said brush, said finger being retractable againstthe bias of said spring, and means to lock said finger in aretractedposition including a detent to which the end of said finger oppositesaid free brush engaging portion may be retracted and against which saidend is yieldably held by said spring when said finger is retracted.-

References Cited in the file of this patent UNITED STATES PATENTS

1. CELLULAR MEANS FOR HOLDING A BRUSH IN CONTACT WITH A COMMUTATORCOMPRISING A SUPPORTING CASE, A BRUSH ENGAGING FINGER MOUNTED IN SAIDCASE AND HAVING A FREE BRUSH ENGAGING PORTION EXTENDING THEREFROM, ASPRING SECURED TO SAID FINGER AND TO SAID CASE ADAPTED TO CAUSE SAIDFINGER TO EXERT A NON-VARIABLE PRESSURE ON THE BRUSH IT IS ADAPTED TOCONTACT WHEN SAID CASE IS SECURED IN JUXTAPOSED RELATION THERETO, ANDMEANS TO LOCK SAID FINGER IN A RETRACTED POSITION IN ORDER TO REMOVE ANDREPLACE THE BRUSH NORMALLY ENGAGED THEREBY INCLUDING GUIDE MEANSSLIDABLY GUIDING SAID FINGER AND PIVOTALLY SECURED TO SAID CASE AND ADETENT ON THE OPPOSITE SIDE OF THE POINT OF PIVOTAL CONNECTION OF SAIDGUIDE MEANS TO SAID CASE FROM SAID BRUSH ENGAGING PORTION TO WHICH ANEND OF SAID FINGER IS MOVABLE AND AGAINST WHICH SAID END IS YIELDABLYHELD BY SAID SPRING WHEN SAID FINGER IS RETRACTED.